It is known to provide an automotive audio system in which, in addition to four speakers being mounted in four door panels, speakers for the vehicle driver are mounted in the headrest of the driver seat so that only the driver can listen to route guidance and traffic congestion information from the navigation system, while allowing other vehicle occupants other than the driver to listen to music being played back on a CD player (refer, for example, to patent document 1).
However, since the sounds from the usual four speakers mounted in the four door panels can also be heard by the driver, there has been the problem that the sounds may become distracting to the driver when the driver is listening to route guidance and traffic congestion information from the navigation system, while on the other hand, sound leakage from the driver seat speakers may disturb the other occupants who are listening to music being played back on a CD player.
It is also known to provide an array speaker system that uses an array speaker which produces sound from a plurality of orderly arranged speaker units, and that controls the directivity of the sound to be output from each individual speaker unit of the array speaker (refer for example to patent document 2). In this system, control can be performed so that sounds from the different speaker units simultaneously arrive at a desired point in space by adjusting the amount of delay of a sound signal to be input to each individual speaker unit.
However, the above system has not been designed by taking into consideration the environment inside a vehicle, nor has it been a system designed for use in any specific frequency range of the sound output signal.
Patent document 1: Japanese Unexamined Patent Publication No. 2005-159913 (FIG. 2)
Patent document 2: Japanese Unexamined Patent Publication No. 2004-363696 (FIG. 7)